Japanese agricultural society is undergoing rapidly declining birth rate and growing proportion of elderly people. That is, while the farming population of the whole country has been declining, the number of agricultural workers aged over sixty has been increased to 2.2 million. Furthermore, in keeping with a crying need for improvement in the ratio of self-sufficiency in food products, farmwork support has been increasingly demanded. Under such circumstances, power assist robot equipment such as a power assist suit is utilized as farmwork support equipment that is not designed for traditional US-style large-scale agriculture mechanization but is adapted to Japanese narrow agricultural land, and is also useful in the invigoration of agriculture in intermontane areas and local revitalization.
There are two types of power assist suits, namely a light-work power assist suit and a heavy-work power assist suit. The light-work power assist suit is used for light-work support, for example, support for lifting, lowering, and transportation of light objects weighing ca. 10 kg or less, including work in a looking-up posture such as pollination, flower removal, picking, bagging, and harvest for fruits such as peaches, Japanese persimmons, mandarin oranges, grapes, and kiwis, and work in a half-sitting posture such as strawberry harvest, and also support for walking and running on the flat ground, slope, and stairs.
The heavy-work power assist suit is used for heavy-work support, for example, support for work in a half-sitting posture to harvest large vegetables such as Japanese white radishes and cabbages, and support for lifting, loading, unloading, and transportation of heavy objects weighing ca. 30 kg such as rice bags and crop containers.
Moreover, power assist suits are, in addition to being used for agricultural purposes, used in factories for work such as transportation of heavy objects and for work in a long-time continuous fixed posture. In addition, power assist suits are used for nursing-care purposes such as transfer of a person from a bed to a wheelchair, and can also be used for rehabilitation, for example, support for walking rehabilitation.
There are two types of drive systems for driving power assist suits, namely a passive system and an active system. Examples of the passive system include a spring-type system and a rubber-type system. Examples of the active system include an electric motor-type system, a pneumatically driving-type system, and a hydraulically driving-type system. Some of the pneumatically driving-type systems employ a pneumatic rubber artificial muscle, a pneumatic cylinder, and a pneumatic rotary actuator (refer to Patent Literatures 1 and 2, for example).
Moreover, examples of assist control systems for power assist suit control include an action pattern reproduction-type system based on sound input or switch input; a system for estimating torque which is to be produced from muscles based on surface electromyogram (EMG) signals (refer to Patent Literature 3, for example); an action pattern reproduction-type system for reproducing action patterns based on surface electromyogram (EMG) signals as trigger signals (refer to Patent Literature 4, for example); and a master-slave control-type system in which a power assist suit is allowed to follow the movement of a user wearing the power assist suit by feedback-controlling a force exerted on the user's wrist or ankle measuring by a sensor (refer to Patent Literatures 2, 5, and 6, for example).